Systematic Review and Meta-Analysis of the Effectiveness of Calcium-Phosphate Coating on the Osseointegration of Titanium Implants

Ca-P coatings on Ti implants have demonstrated good osseointegration capability due to their similarity to bone mineral matter. Three databases (PubMed, Embase, and Web of Science) were searched electronically in February 2021 for preclinical studies in unmodified experimental animals, with at least four weeks of follow-up, measuring bone-to-implant contact (BIC). Although 107 studies were found in the initial search, only eight experimental preclinical studies were included. Adverse events were selected by two independent investigators. The risk of bias assessment of the selected studies was evaluated using the Cochrane Collaboration Tool. Finally, a meta-analysis of the results found no statistical significance between implants coated with Ca-P and implants with etched conventional surfaces (difference of means, random effects: 5.40; 99% CI: -5.85, 16.65). With the limitations of the present review, Ca-P-coated Ti surfaces have similar osseointegration performance to conventional etched surfaces. Future well-designed studies with large samples are required to confirm our findings.

Controlled release of BMP-2 from titanium with electrodeposition modification enhancing critical size bone formation

In this study, a porous Ti-alloy based implant with an interconnected channel structure (MAO-CaP-BMP2) is fabricated using a method combining 3D printing, microarc oxidation (MAO) treatment, and co-precipitation of Ca,P layer with BMP-2 technique. The macroporous structure with pore size of 600 μm made by 3D printing not only enhances the ingrowth of cells but also allows the formation of blood vessels inside the implant. As a result, the new bond formation is promoted. In addition, the microporous dioxide layer formed on the implant surface by MAO provides the sites for co-precipitation of Ca,P layer with BMP-2. The microstructure allows the prolonged release of BMP-2. Our results show that a sustained release of BMP-2 over 35 days is achieved for MAO-CaP-BMP2 group longer than Ti without MAO modification group and without Ca,P electrochemical deposition group. The slow release of BMP-2 at the bone/implant interface for a long period of time leads to enhancement of the osseointegration between the implant and surrounding bones. This result indicates that MAO-CaP-BMP2 is a good candidate of growth factor carrier. Successful regeneration of bone requires the concomitant processes of osteogenesis and neovascularization. MAO-CaP-BMP2 modified Ti-alloy implant is both osteoinductive and osteoconductive which can create better osteogenesis and angiogenesis. As a result, it can enhance bone formation.

Effects of Biomineralization on Osseointegration of Pure Titanium Implants in the Mandible of Beagles

PURPOSE

The purpose of this study was to investigate the effect of a biologically active dental implant surface (treated with sandblasting and acid etching [SLA] followed by immersion in simulated body fluid [SBF]) on osseointegration.

MATERIALS AND METHODS

We randomly divided 9 healthy adult male beagles (aged 8 months; body weight, 12 kg) into 3 groups: machined, SLA, and SLA-biomineralization (SLA-Bio). Six pure titanium implants (diameter of 3.5 mm and length of 8 mm) were used in the mandible of each dog after observation of the surface morphology, as well as analysis of the composition of the surface elements by scanning electron microscopy-energy dispersive x-ray spectroscopy. At 4, 8, and 12 weeks after implantation, animals were euthanized to collect the mandibles so that we could perform the removal torque test to evaluate the implant stability in bone and histomorphometry to analyze the implant-bone osseointegration.

RESULTS

Scanning electron microscopy results showed that uniformly distributed sponge-like structures were found on the SLA-treated surface and an apatite layer was observed on the SLA-SBF-treated surface (SLA-Bio group). In the energy dispersive x-ray spectroscopy analysis, the elements titanium, oxygen, carbon, calcium, and phosphorus were found on the surfaces of the SLA-Bio group, whereas titanium was the only element found in the other groups. The removal torque test showed that the peak removal torque values of the 3 groups increased gradually with the passage of time, and the peak removal torque values of the SLA-Bio group were significantly higher than those of the other groups (P < .01) at 4, 8, and 12 weeks after implantation. Histomorphometric analysis showed that osseointegration was being enabled more rapidly in the SLA-Bio group, as well as that the mineral apposition rate and percentage of bone-to-implant contact of the SLA-Bio group were higher than those of the remaining groups at 4, 8, and 12 weeks after implantation (P < .01).

CONCLUSIONS

Treating titanium implants with SLA-SBF can improve osseointegration as well as increase the interfacial shear strength.

Removal torque of nail interlocking screws is related to screw proximity to the fracture and screw breakage

Studies have shown that titanium implants can be challenging to explant due to the material's excellent biocompatibility and resulting osseointegration. Clinically, titanium alloy nail interlocking screws may require removal to dynamize a construct or revise the nail due to nonunion, infection, pain, or periprosthetic fracture. This study was designed to determine what variables influence the removal torque for titanium alloy interlocking screws. An intramedullary nail with four interlocking screws was used to stabilize a 1-cm segmental femoral defect in a canine model for 16 weeks. The animals were observed to be active following a several-day recovery after surgery. In six animals, the femora and implanted nail/screws were first tested to failure in torsion to simulate periprosthetic fracture of an implant after which the screws were then removed. In four additional animals, the screws were removed without mechanical testing. Both intraoperative insertional and extraction torques were recorded for all screws. Mechanical testing to failure broke 10/24 screws. On average, the intact screws required 70% of the insertional torque during removal while broken screws only required 16% of the insertional torque (p < 0.001). In addition, intact screws closer to the fracture required 2.8 times more removal torque than the outboard distal screw (p < 0.005). On average, the angle of rotation to peak torque was ∼80°. The peak axial load did not significantly correlate with the torque required to remove the screws. On average, the removal torque was lower than at the time of insertion, and less torque was required to remove broken screws and screws remote to the fracture. However, broken screws will require additional time to retrieve the remaining screw fragment. This study suggests that broken screws and screws in prematurely active patients will require less torque to remove.

Biomechanical and histological evaluation of four different titanium implant surface modifications: an experimental study in the rabbit tibia

OBJECTIVES

This study presents a biomechanical comparison of bone response to commercially pure titanium screws with four different types of surface topographies placed in the tibial metaphysis of 30 rabbits.

MATERIALS AND METHODS

One hundred twenty implants were tested double-blinded: (a) blasted, acid-etched, and discrete crystal deposition (DCD), (b) blasted, (c) acid-etched, and (d) blasted and acid-etch. Resonance frequency analysis (RFA/ISQ), reverse torque values (RTV), and bone-to-implant contact (BIC) were measured at the time of implant insertion (day 0), 15, 28, and 56 days of healing.

RESULTS

All groups tested demonstrated increased RFA/ISQ and RTV results over the time course. At 15 days, the blasted, acid-etched, and DCD group demonstrated a non-significant trend toward higher values when compared to the blasted and etched group (33.0 ± 16 vs. 26.3 ± 12 Ncm, p = .16). At 56 days, the groups utilizing blasting to create additional surface roughness (Sa > 1 micron) showed a statistical significant difference in RTQ versus the non-blasted group (38.5 ± 14 vs. 29.5 ± 9 Ncm, p = .03).

CONCLUSIONS

Within the limitations of this study, only the increase in surface roughness (Ra > 1) at 56 days demonstrated statistically significant effects on RTQ. Other additional surface features, such as sub-micron scale DCD, demonstrated improved healing trends but without significance for clinical applications.

The osseointegration behavior of titanium-zirconium implants in ovariectomized rabbits

OBJECTIVE

The aim of this study is to compare the osseointegration behavior of titanium (Ti) and titanium-zirconium (TiZr) implants in ovariectomized (OVX) rabbits.

MATERIALS AND METHODS

Twelve ovariectomized New Zealand rabbits submitted to a hypocalcic diet and 12 sham-aged rabbits were used. After the bone mass loss induction period, TiZr or Ti implants both benefiting from a SLActive surface treatment were randomly inserted in the tibia and femur of each animal. The total of 24 rabbits were divided in four groups (n = 6): SHAM + Ti, OVX + Ti, SHAM + TiZr,OVX + TiZr. The animals were respectively sacrificed 3 and 6 weeks after dental implant placement. Six implants in each group at each time point were subjected to removal torque testing, and the remaining implants were prepared for histomorphometric analysis.

RESULTS

At the end of the healing period, all implants were osseointegrated. The removal torque value of the SHAM-TiZr group was significantly higher than those of the SHAM-Ti group (P < 0.001). The removal torque of the OVX-Ti group was significantly lower than those of the OVX-TiZr group. All groups demonstrated an increase in the peak torque value after 6 weeks: 46.0 and 50.8 Ncm for the OVX and the SHAM animals, respectively, in the case where Ti implants were used. When TiZr implants were inserted, the values reached 60.7 and 76.2 Ncm with a similar group configuration. The BIC and the BA/TA analysis showed an increase between week 3 and 6 in the case of nonovariectomized animals. From week 3 to 6, the BIC went from 37.1 ± 14.3 to 47.7 ± 8.7 for the SHAM + Ti group and from 37.6 ± 10.9 to 50.4 ± 11 for the SHAM + TiZr group. The BIC values were not significantly different between groups.

CONCLUSION

The parameters intended to be representative of the bone morphology (BIC & BATA) did not help to discriminate between Ti and TiZr which appeared to behave similarly in this experimental model. However, the removal torque values for the TiZr group were statistically higher than those of the Ti group in both the SHAM and the ovariectomized animals. That likely reflected an increased quality of bone around the TiZr implants.

Influence of nanocoated calcium phosphate on two different types of implant surfaces in different bone environment: an animal study

OBJECTIVE

The purpose of this study was to evaluate the osseointegration of two different types of surfaces, smooth and roughened surface implants nanocoated with calcium phosphate (CAP) around different bone environment.

MATERIALS AND METHODS

Five male mongrel dogs were used in this study. The premolars and molars were extracted on both sides of the mandible. Eight weeks after extraction, implants were submerged on both sides of the mandible. On the left, CAP nanocoated roughened surface (RCAP) implants were installed whereas, the CAP nanocoated smooth surface (SCAP) implants were installed on the right side. The control group had no defect, on the other hand, three-wall intrabony defects were surgically created adjacent to the implant in the experimental group. The dogs were sacrificed after 12 weeks.

RESULTS

Histological and histomorphometrical analysis were performed with the specimen. The SCAP and RCAP implants showed good osseointegration with no statistical significance in the control group. Histologically, the SCAP group showed little resolution of the defect compared with the RCAP group. In the experimental groups, there was a significant difference in defect fill between SCAP and RCAP.

CONCLUSION

Within the limits of our study, it can be concluded that SCAP and RCAP implants show no difference in sufficient bone area whereas, CAP nanocoating on roughened implant surface may enhance osseointegration in deficient bone environment.

Osteoblast response to puerarin-loaded porous titanium surfaces: an in vitro study

Recent studies demonstrate puerarin stimulates bone formation, suggesting its potential application in dental implantology field. The aim of this study was to investigate effects of puerarin-loaded titanium surfaces on the promotion of osteogenesis in preosteoblasts (MC3T3-E1). Puerarin was prepared onto titanium surfaces with varying concentration (10(-9) M, 10(-8) M, 10(-7) M, and 10(-6) M) by biomimetic calcium phosphate deposition process. Surface characteristics were performed by field-emission scanning electron microscope (FSEM), X-ray diffractometer (XRD), and Fourier transform infrared spectroscopy (FTIR). Puerarin concentration in the coatings was performed by High-performance liquid chromatograph (HPLC) analyses. FSEM observation showed puerarin concentration influenced formation of sharp flakes in the coating. The size of flakes decreased with increase of puerarin concentrations. XRD and FTIR examinations demonstrated the puerarin concentration did not affect the chemical compositions of coatings, which composed of octacalcium phosphate (OCP). Puerarin concentration on the surfaces of 10(-8) M group was 10.22 ± 0.32 ng/cm(2) . Puerarin had an increased effect on MC3T3-E1 ALP activities. Significant differences were found in 10(-8) and 10(-7) M groups on day 4, 10(-8) , 10(-7) , and 10(-6) M groups on day 7, and 10(-8) on day 14. In Type I collagen synthesis assay, 10(-9) and 10(-8) M on day 7, 10(-8) on day 14 showed significant differences compared with control group. Furthermore, this stimulatory effect of puerarin was also observed in osteocalcin release assay (p < 0.05, at 10(-8) M and 10(-7) M, maximal at 10(-8) M). These results indicate puerarin-loaded titanium surfaces promote accelerated osteogenic differentiation of preosteoblasts, which has the potential to improve the nature of osseointegration.

Osseointegration of two different phosphate ion-containing titanium oxide surfaces in rabbit cancellous bone

OBJECTIVE

This study assessed the osseointegration of grit-blasted titanium (Ti) implants with a hydrophilic phosphate ion-incorporated oxide surface in rabbit cancellous bone, and compared its bone healing with commercially available phosphate-incorporated clinical implants obtained by micro-arc oxidation (TiUnite, TU implant).

MATERIAL AND METHODS

The hydrophilic phosphate-incorporated Ti surface (P implant) was produced by hydrothermal treatment on grit-blasted moderately rough-surfaced clinical implant. The TU surface was used as a control. The surface characteristics were evaluated by field emission-scanning electron microscopy, X-ray photoelectron spectroscopy, optical profilometry, and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Thirty-two threaded implants with lengths of 10 and 3.3 mm diameter (16 P implants and 16 TU implants) were placed in the femoral condyles of 16 New Zealand White rabbits. Histomorphometric analysis, removal torque tests, and surface analysis of the torque-tested implants were performed 4 weeks after implantation.

RESULTS

The P and TU implants displayed micro-rough surface features with similar Ra values at the micron-scale. ICP-AES analysis revealed that both the P and TU implants released phosphate ions into the solution. The torque-tested P and TU implants exhibited a considerable quantity of bone attached to the surface. The P implants exhibited significantly higher bone-implant contact percentages, both in terms of the all threads region and the total lateral length of implants compared with the TU implants (P < 0.01), but no statistical difference was found for the removal torque values.

CONCLUSION

These results suggest that the phosphate-incorporated Ti oxide surface obtained by hydrothermal treatment achieves rapid osseointegration in cancellous bone by increasing the degree of bone-implant contact.